Aqueous Glycol Research Articles

INVESTIGATION OF THE HEAT CAPACITIES OF NANOFLUIDS BASED ON NANOPARTICLES OF Al2O3, TiO2 AND CuO BY THE ADDITIVE METHOD

This study investigates the thermal properties of nanofluids, with a particular focus on their heat capacity when various nanoparticles are integrated into a base fluid. Nanofluids, which are composed of nanoparticles dispersed within a base fluid, are of significant interest due to their enhanced thermal characteristics compared to traditional fluids. The research employs the additive method, a widely used technique for estimating the effective heat capacity of nanofluids. This method posits that the total heat capacity of a nanofluid can be approximated by summing the contributions of each component according to its volume or mass fraction. This research represents the effect of nanopartilces concentration (1wt.%, 3 wt.%, 5 wt.%) on effective heat capacity of TiO2 based nanofluid. The analysis reveals that key factors influencing the heat capacity of a nanofluid, as determined by the additive method, include the heat capacities of the individual components and the concentration of the nanoparticles. Specifically, the greater the disparity in heat capacities between the base fluid and the nanoparticles, and the higher the nanoparticle concentration, the more the nanofluid's heat capacity shifts toward that of the nanoparticles. The calculations in this study indicate that the most significant decrease in heat capacity occurs in a nanofluid containing 5 wt.% Al2O3 nanoparticles with water as the base fluid. Conversely, the smallest reduction is observed in a nanofluid with 1 wt.% Al2O3 nanoparticles in a 50% aqueous ethylene glycol solution.

Investigation of the impacts of several diols on the phase behavior and physico-chemical quantities associated with the Triton X-100 and antidiabetic drug mixture

Drug-surfactant interaction phenomena have received popularity in the pharmaceutical industry and technological sectors from the view point of wider applications. Herein, we aimed to investigate the clouding behavior and various thermodynamic properties of Triton X-100 (TX-100) and metformin hydrochloride drug (MNH; an antidiabetic drug) mixture in the attendance of diols followed by the cloud point measurement technique. The dosage form of metformin hydrochloride drug controls the glucose level in the blood. The different types of diols, i.e., ethylene glycol (EG), 1,2-propylene glycol (1,2-PrG), 2,3-butanediol (2,3-BD), and 1,5-pentanediol (1,5-PD) were uniformly used in this inspection. The effect of diols, with the variation of their concentrations on the clouding behavior of TX-100 + MNH mixture having fixed content of TX-100 (92.7 mmol kg−1) and MNH drug (2 mmol kg−1), were examined. The most enhanced CP value was experienced in the aqueous 1,5-PD medium, whereas the lowest CP value was observed in the aqueous EG medium. The CP values were recorded for the working system under the effect of changing concentrations of diols, which were observed to follow the sequential order: CPH2O+1,5−PD>CPH2O+2,3−BD>CPH2O+1,2−PrG>CPH2O+EG. The clouding progression of the working system was realized to be nonspontaneous as concluded from the positive free energy change (ΔGco) values. The positive and negative values of enthalpy (ΔHco) and entropy (ΔSco) change were documented, respectively, at the low and high concentrations of diols. The hydrophobic interactions amongst different components are predominant at the low concentrations of diols, whereas the electrostatic interactions are leading factors at the high concentrations of diols. Enthalpy-entropy compensation parameters were computed and interpreted with proper perceptive. The outcomes of this observation may be effective and helpful in the various industrial sectors, especially in the drug carrier system in the pharmaceutical arena.

Anti-SARS-CoV-2 activity of microwave solvolysis lignin from woody biomass

The global pandemic caused by the novel coronavirus, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has had profoundly detrimental effects on our society. To combat this highly pathogenic virus, we turned our attention to an abundant renewable natural aromatic polymer found in wood. Through a chemical modification of Eucalyptus and Japanese cedar wood via acidic microwave solvolysis in equivolume mixture of 2 % (w/w) aqueous H2SO4, ethylene glycol, and toluene at 190 °C. Subsequently, we separated the resulting solvolysis products through extractions with toluene, ethyl acetate, and ethanol. Among these products, the ethyl acetate extract from Eucalyptus wood (eEAE) demonstrated the highest inhibition effects against the novel SARS-CoV-2. We further divided eEAE into four fractions, and a hexane extract from the ethanol-soluble portion, termed eEAE3, exhibited the most substantial inhibitory rate at 93.0 % when tested at a concentration of 0.5 mg/mL. Analyzing eEAE3 using pyrolysis gas chromatography–mass spectrometry revealed that its primary components are derived from lignin. Additionally, 1H–13C edited-heteronuclear single quantum coherence nuclear magnetic resonance analysis showed that the solvolysis process cleaved major lignin interunit linkages. Considering the abundance and renewability of lignin, the lignin-derived anti-SARS-CoV-2 agent presents a promising potential for application in suppressing infections within our everyday environment.

Thermal Stability of Dispersions of Amino-Functionalized Silica in Glycol and in 50-50 Aqueous Glycol.

Dispersions of amino-functionalized silica in ethylene glycol (EG) and in aqueous glycol show excellent stability at room temperature. Stability at elevated temperatures would be much desired with respect to their potential application as heat-transfer fluids. Amino-functionalized silica was dispersed in EG and in 50-50 aqueous EG by mass. HCl and acetic acid were added to enhance the positive ζ potential. The dispersions were stored at 40, 60, 80, and 100 °C for up to 28 days, and ζ potential and apparent particle radius were studied as a function of elapsed time. The particles showed a positive ζ potential in excess of 40 mV (Smoluchowski), which remained unchanged for 28 days. Such a high absolute value of ζ potential is sufficient to stabilize the dispersion against flocculation and sedimentation. The apparent particle radius in acidified dispersions was about 70 nm, and it was stable for 28 days. The particles were larger in pH-neutral dispersions. The apparent particle radius was about 80 nm in fresh dispersions and it increased on long storage at 80 and 100 °C.

Prediction of bubble departing diameter in pool boiling of mixtures by ANN using modified ReLU

In this research, bubble departure diameter in pool boiling have been measured in aqueous amine and ethylene glycol solutions for various concentrations. The experimental data have been compared with major existing predictive correlations. It is shown that the effect and identity of the independent variables on bubble diameter proposed in the previous studies are inconsistent. The predictions of different correlations have on average a deviation of about 40% from the experimental data. This is mainly due to the complicated interactions between bubbles on the heterogeneous boiling medium, which provides a complex condition. This complexity limits any mathematical modelling of the forces acting on the developing bubbles. Particularly in liquid solutions, where mass transfer by back diffusion through micro-sub-layers adds further complexity. In this work, the classical artificial neural network, ANN, with rectified linear unit, ReLU, activating function, AF, has been modified. This modification is based on adding a numerical matrix to each layer to adjust the slope of AF for each neuron independently. The addition of this parameter, together with the adjustment of the bias matrix, makes the activation function more flexible than the classical ReLU. To find the tuning parameters, a genetic algorithm was implemented instead of the back-propagation technique. It is shown that the predictions of the trained ANN with modified ReLU AF agree within an absolute average error of 10%, which is equal to the total uncertainty of the measurements. Prediction of bubble departing diameter in boiling phenomena is a key parameter for accurate design, operation and optimisation in many industrial systems.

Complete thermal characterization of liquids by front photopyroelectric configuration using the reference sample method

We explored the use of the front photopyroelectric (FPPE) configuration and the reference sample method to determine the thermal properties of liquid samples such as extra virgin olive oil and aqueous glycerol (GL), ethylene glycol (EG), and sodium chloride (NaCl) solutions. The thermal diffusivity (α) and thermal conductivity (k) were determined from photopyroelectric phase and amplitude signals, respectively, using water as a reference. The thermal effusivity (e) and volumetric heat capacity (ρc) were also determined based upon both obtained thermal properties. All thermal properties of GL and EG in aqueous solutions decrease as their volume fraction increases at an average rate of 5% for concentrations higher than 20% and between 23% and 10% for concentrations less than 20%. The Matvienko and Mandelis’ model for α and our proposed expression for ρc described this trend with a reliable approximation to the experimental data with R 2 about 0.97 and 0.99, respectively. Moreover, the frequency of a specific angle is proportional to α as established by the theory for the phase signal for thermally thick samples. In the case of aqueous NaCl solutions, the α and k values were slightly below 4.6% and 3% from water values reported at room temperature. The proposed method allows the simultaneous determination of α and k by using only the FPPE configuration with test and reference liquid samples, reducing time and uncertainties from the use of more than one experimental setup, and providing the complete thermal characterization.

Liquid-Vapor Interface of Aqueous Ethylene Glycol Solutions: A Molecular Dynamics Study.

While the organic constituent in an aqueous binary solution enriches its liquid-vapor (l-v) interface, the extent of enrichment can depend nonlinearly on its mole fraction. A microscopic quantification and rationalization of this behavior are crucial to understand the dependence of properties such as surface tension and evaporation rate of the solution on its composition. Extensive all-atom molecular dynamics simulations of aqueous ethylene glycol (EG) solutions show that the composition of the solution at the l-v interface deviates the most from that in the bulk solution at an EG mole fraction of 0.3. The population of EG molecules with their central C-C dihedral in the gauche conformation was found to be higher at the l-v interface than that in the bulk solution to facilitate the orientation of its hydrophobic methyl groups toward the vapor phase. Free energy calculations reveal that in dilute EG solutions, an EG molecule is most stable at the l-v interface. The behavior of vapor pressure in aqueous EG solutions is ideal and follows Raoult's law, while in contrast, the aqueous solution of dimethyl sulfoxide does not. A rationale for the same is provided through the orientational distribution of interfacial water molecules in the respective solutions.

Solubility Enhancement and Formulation Development of an Oral Film of Ondansetron Hydrochloride Monohydrate using Mix-solvency Concept

This research paper presents the formulation and evaluation of ondansetron hydrochloride monohydrate oral film using the mix-solvency concept. Ondansetron hydrochloride monohydrate a selective serotonin receptor antagonist is commonly prescribed to prevent chemotherapy or surgery-induced nausea and vomiting. The aim of the study was to enhance the solubility of ondansetron hydrochloride monohydrate which has been enhanced by the blend of varying aqueous solubilizers poly ethylene glycol, niacinamide, and caffeine. The oral film formulation was prepared using a solvent casting method, incorporating polymers, plasticizers and different solvents. Various formulation variables, including solvent type and concentration, polymer-to-plasticizer ratios, and drug loading, were optimized systematically the resulting oral film was investigated for various parameters such as thickness, drug content, disintegration time, folding endurance and surface pH. The % in-vitro release of drug of the best two formulations F3 and F5 was 99.70 and 96.62%, respectively.

Probing coumarin solubility and solvation energetics in diverse aqueous–organic solutions across a temperature range: A debut exploration

In this research, an investigation was conducted to explore the solubility of coumarin in both aqueous solutions and binary mixtures, specifically in pure and aqueous ethylene glycol (EG), aqueous 2-methoxyethanol (ME), and aqueous 1,2-dimethoxyethane (DME). Solubility experiments were conducted first time using UV–Vis spectroscopy at a temperature range of 288.15–313.15 K at a pressure of 0.1 MPa for the current solute solvent systems. A digital thermostat was used to maintain the precise temperature. The findings indicated that coumarin exhibits its highest solubility in pure DME (3.0824 mol·kg−1) and its lowest solubility in pure EG (0.0169 mol·kg−1) across all temperatures. Various solvation parameters were calculated to enable the determination of solvation-related thermodynamic properties. The experimental results were used to evaluate various thermodynamic parameters including solution Gibbs free energies, transfer Gibbs free energies associated with cavity and dipole–dipole interactions, enthalpy of transfer, and non-covalent transfer energies. The focus of this research was on to provide insights into the thermodynamics of coumarin-like organic molecules when dissolved in solutions. The study aimed to contribute valuable information regarding the stability of coumarin, particularly in relation to non-covalent interactions. These insights have potential to influence the manufacturing and purification processes, thereby expanding its potential applications across various industries.

Antimultidrug-resistant bacterial activity of microwave solvolysis lignin from woody biomass

Drug-resistant bacteria are a serious concern for human health. Thus, protective substances need to be urgently developed to inhibit the propagation of such bacteria in living environments. We herein report about antibacterial activity of lignin, which was developed via chemical alteration of native lignin in wood. Japanese cedar (Cryptomeria japonica) wood was degraded via microwave solvolysis in an equivolume mixture of 2 % (w/w) aqueous sulfuric acid, ethylene glycol, and toluene at 190 °C for 60 min and fractionated via extraction with toluene, ethyl acetate, and ethanol. The ethyl acetate extract (jEAE) exhibited ≥ 98.5 % inhibitory activity against the drug- and multidrug-resistant strains of Streptococcus pneumoniae. jEAE also exhibited strong inhibitory activity against two nondrug-resistant S. pneumoniae and one Streptococcus pyogenes strains. Lignin-derived monomers having guaiacyl nuclei were detected as major fragments using pyrolysis gas chromatography–mass spectrometry (GC–MS), indicating that jEAE is a solvolysis lignin. In 1H–13C-edited heteronuclear single quantum coherence nuclear magnetic resonance (NMR), signals of guaiacyl nuclei were observed, but those from side chains of β-O-4, β-5, and 5–5/4-O-β substructures disappeared. 31P NMR revealed that jEAE possesses lower and higher amounts of aliphatic and phenolic OH groups, respectively, than milled wood lignin. The high antidrug-resistant bacterial activity of the structure-altered lignin provides a new approach for suppressing the growth of drug-resistant bacteria using lignocellulosic biomass.

Volumetric, compressibility and conductometric studies of L-histidine in aqueous poly ethylene glycol solutions at different temperatures

Volumetric, compressibility and conductometric studies of L-histidine in aqueous poly ethylene glycol solutions at different temperatures

Roles of hydrogen bonding interactions and hydrophobic effects on enhanced water structure strength in aqueous alcohol solutions

The structure and dynamics of water in aqueous alcohol solutions were explored using two-dimensional Raman correlation spectroscopy (2D Raman-COS) combined with the density functional theory (DFT). The spectral changes in the H–O–H bending and O:H stretching modes demonstrated that ethanol and n-propanol induced an enhancement of the water structure compared to methanol. The extent of this effect was related to the length of the alkyl chain. Comparative studies with aqueous ethylene glycol solution revealed that an enhanced water structure stemmed mainly from hydrophobic effects rather than hydrogen bonding (H-bonding) interactions. Alcohol-induced water-specific structural transitions were further analyzed using 2D Raman-COS, which showed that the free OH and strong H-bond structure of water respond preferentially to changes in alcohol content, inducing a transition in the weak H-bond structure of water. In addition, the 2D Raman-COS results indicated that the CH3 stretching mode of alcohol responds preferentially to variations in water content compared to other C–H vibrational modes. Finally, the details of the alcohol-induced water structural transitions were calculated using DFT. The 2D Raman-COS combined with DFT calculations provided insight into alcohol-induced water structural transitions and can be easily extended to other studies of water-organic chemistry.

Ruthenium-Catalyzed Transformation of Ethylene Glycol for Selective Hydrogen Gas Production in Water

We developed an efficient process for producing hydrogen gas from aqueous ethylene glycol (EG) at 90–160 °C over a ruthenium catalyst. We achieved a high yield of hydrogen gas (up to 3.0 n(H2)/n(EG)) and formic acid (85% yield) from ethylene glycol in aqueous alkaline medium at 110 °C, where the role of reaction temperature and base concentration was found to be critical in achieving a high yield of H2. The chemical and morphological properties of the synthesized ruthenium catalyst were established using P-XRD, TEM, XPS, and other techniques. Advantageously, the ruthenium catalyst exhibited appreciably high long-term stability for over 70 h, generating ca. 290 L of H2 per gram of Ru with a yield of 1035 L of H2 per L of ethylene glycol.

Hydrogen-Bond Dynamics and Water Structure in Aqueous Ethylene Glycol Solution via Two-Dimensional Raman Correlation Spectroscopy

The hydrogen-bond (H-bond) dynamics and water structural transitions in aqueous ethylene glycol (EG) solution were investigated on the basis of concentration- and temperature-dependent two-dimensional Raman correlation spectroscopy (2D Raman-COS). At room temperature, EG-induced enhancement of the water structure when the EG/water molar ratio is less than 1:28 resulted from the hydrophobic effect around the methylene groups of EG. The decrease in the temperature caused an enhancement of the Raman peak at about 3200 cm-1, representing an increase in the orderliness of water molecules. Further analysis of the water-specific structures by 2D Raman-COS reveals that the strong H-bond structure preferentially responds to external perturbations and induces a weak H-bond structural transition in water. Finally, EG-induced water structural transitions were calculated by the density functional theory (DFT). Hopefully, 2D Raman-COS combined with DFT calculations would advance the study of solute-induced water structural transitions in water-organic chemistry.

Zeta Potential of Nanosilica in 50% Aqueous Ethylene Glycol and in 50% Aqueous Propylene Glycol.

A sufficient amount of ionic surfactants may induce a zeta potential of silica particles dispersed in water-glycol mixtures of about 100 mV in absolute value. Nanoparticles of silica were dispersed in 50-50 ethylene glycol (EG)-water and 50-50 propylene glycol (PG)-water mixtures, and the zeta potential was studied as a function of acid, base, and surfactant concentrations. The addition of HCl had a limited effect on the zeta potential. The addition of NaOH in excess of 10-5 M induced a zeta potential of about -80 mV in 50% EG, but in 50% PG the effect of NaOH was less significant. The addition of CTMABr in excess of 10-3 M induced a zeta potential of about +100 mV in 50% EG and in 50% PG. The addition of SDS in excess of 10-3 M induced a zeta potential of about -80 mV in 50% EG and in 50% PG. Long-chained analogs of SDS were even more efficient than SDS, but their application is limited by their low solubility in aqueous glycols.

Pre-swelling of FAA3 membranes with water-based ethylene glycol solution to minimize dimensional changes after assembly into a water electrolyser: Effect on properties and performance

Stability of membranes in electrolysers is challenged by dimensional changes, when dry membranes are assembled and wetted when the electrolyser starts. Assembling wet membranes is challenging because water evaporates during handling. To minimize dimensional changes, FAA3 membranes are pre-swollen in aqueous ethylene glycol (EG, boiling point 197°C). Membranes partially dissolve in 100 vol% EG, and swell excessively in 70 vol%. Swelling in 50 vol% shows smallest dimensional changes during handling (shrink) and re-immersion in KOH solution (swelling, mimicking start of the electrolyser). These membranes show about 30% higher conductivity (ca. 65 mS cm−1). Tensile strength and Young’s Modulus decrease exponentially with the amount of absorbed EG solution, while elongation at break increases. In addition to the improved dimensional stability during handling, EG treated membranes perform better in the electrolyser than untreated membranes. In a stability test over 120 h at 250 mA/cm2, all membranes show an initial drop in the cell voltage and then stabilize.

Ethylene glycol energetically disfavours oligomerization of pseudoisocyanine dyestuffs at crowded concentrations.

The intriguing role of the intracellular crowded environment in regulating protein aggregation remains elusive. The convolution of several factors such as the protein sequence-dependence, crowder's shape and size and diverse intermolecular interactions makes it complex to identify systematic trends. One of the ways to simplify the problem is to study a synthetic model for self-assembling proteins. In this study, we examine the aggregation behaviour of the cationic pseudoisocyanine chloride (PIC) dyestuff which is known to self-assemble and form fibril-like J-aggregates in aqueous solutions, similar to those formed by amyloid-forming proteins. Prior experimental studies have shown that polyethylene glycol impedes and Ficoll-400 promotes the self-assembly of PIC dyes. To achieve molecular insights, we examine the effect of crowding by ethylene glycol on the solvation thermodynamics of oligomerization of dyes into H-type and J-type oligomers using extensive molecular dynamics simulations. The binding free energy calculations show that the formation of J-oligomers is more favourable than that of H-oligomers in water. The stability of H- and J- tetramers and pentamers decreases in crowded solutions. The formation of oligomers is supported by the favourable change in dye-solvent interaction energy in both pure water and aqueous ethylene glycol solution although it is opposed by the reduced dye-solvent entropy. Ethylene glycol, as a molecular crowder, disfavours the H- as well as J-oligomerization via preferential binding to the dye oligomers. An unfavourable change in dye-crowder and dye-dye interaction energy on dye association makes the H-oligomer formation less favourable in crowded solution than in pure water solution. In the case of J-oligomers, however, the unfavourable change in dye-crowder interaction energy primarily contributes to making total dye-solvent energy unfavourable. The results are supported by isothermal titration calorimetry measurements where the binding of ethylene glycol to PIC molecules is found to be endothermic. The results provide an emerging view that a crowded environment can disfavour self-assembly of PIC dyes by interactions with the oligomeric states. The findings have implications in understanding the role of a crowded environment in shaping the free energy landscapes of proteins.

Solubility modeling, dissolution and solvation thermodynamics, and solute–solvent interactions of diflufenican in aqueous aprotic and protic cosolvents

Electrostatic characteristics of acidity and basicity of the diflufenican molecule were uncovered by examining the Hirshfeld surface and the electrostatic potential surface, respectively. When it comes to nucleophilic and electrophilic assault, the >NH, =O, and -O- groups are where it is at. Diflufenican-solvent interactions were shown using an independent gradient model based on Hirshfeld partition analysis. Under 101.2 kPa, the isothermal saturation technique was used to experimentally obtain the diflufenican solubility in mixtures of isopropanol/methanol + water and ethyl acetate + ethanol across the temperature range from 278.15 to 323.15 K. Diflufenican was more soluble in ethyl acetate + ethanol blends than alcohol + water blends at the same temperature and cosolvent composition. Maximum relative average deviation of 9.57 percent was obtained using the Jouyban-Acree and modified van't Hoff-Jouyban-Acree models of correlation. The literature-reported solubility of diflufenican in ethylene glycol (EG), ethanol, propylene glycol (PG), and N,N-dimethylformamide (DMF) + water, as well as our determined in ethyl acetate + ethanol and methanol/isopropanol + water at 298.15 K, were all investigated using an extended Hildebrand solubility parameter approach. The local mole fractions of diflufenican in the seven solutions were also investigated using the inverse Kirkwood-Buff integrals technique. Preferential solvation of diflufenican by PG, ethanol, DMF, methanol, and isopropanol in aqueous solutions and by ethyl acetate in ethyl acetate + ethanol solutions was observed. Diflufenican in aqueous EG mixes was not preferentially solvated by EG. Results and discussion of the enthalpy–entropy compensation features of dissolution were reached.

Fast quantification of water content in glycols by compact 1H NMR spectroscopy

Glycols are key chemicals for many applications in different fields of activities. Being highly hydroscopic, glycols contain usually water. The presence of water, even in tiny amounts, can affect their chemical and physical properties. Therefore, the accurate determination of water content is essential for any intended applications. In this context, a novel method using low-field Nuclear Magnetic Resonance (NMR) spectroscopy is introduced. The proposed approach offers a straightforward, fast, low-cost, and versatile solution for water quantification in glycols without the need for reagents or calibration data. It is demonstrated by quantifying the water concentration up to 11 wt% in aqueous ethylene glycol (EG) and triethylene glycol (TEG) mixtures with the help of lineshape analysis of the corresponding proton spectra. The limit of detection, achieved within 1 min of measuring time, was 0.05 wt% for water in EG and 0.15 wt% in TEG. The excellent agreement between the NMR results and those from the Karl-Fischer titration indicates that the proposed NMR-based approach has a great potential to be used as an alternative to the Karl-Fischer method. In addition, it is expected that the same methodology can be applied for water quantification in more complex glycolic solutions and other mixtures.

Formation of smooth anodic nanoporous iron oxide film for enhancing photocathodic protection on plain carbon steel

It is essential to fabricate smooth nanoporous iron oxide film with fewer defects on plain carbon steel (CS) to improve photocathodic protection of the film in corrosive media. For that, high temperature annealing heat treatment was chosen to manipulate the metallographic structure of CS in the muffle furnace at 900 °C with the duration of 30 min. Following that, the annealed CS was anodized in a mixture of aqueous ammonium fluoride solution and ethylene glycol to fabricate smooth nanoporous oxide film on CS. Finally, as-anodized oxide film was calcinated at 450 °C for 4 h in nitrogen atmosphere to form crystalline iron oxide film. Several electrochemical techniques were applied to analyze the photoelectron property and photocathodic protection performance of nanoporous iron oxide films. On the contrary, rough nanoporous iron oxide film with more striking defects was fabricated on untreated (no annealed) CS by using the same anodization and calcination processes. The results show that the metallographic structure of annealed CS behaved more uniform ferrite grains and fewer pearlite precipitate than untreated CS. Thereby, a smooth nanoporous iron oxide film with fewer defects formed on annealed CS. On the contrary, a rough nanoporous iron oxide film with more defects, such as dimples and cracks were fabricated on untreated CS. Both of iron oxide films were composed of hematite as the main phase and magnetite as the secondary phase. Therefore, the smooth iron oxide film displayed comparatively better conductivity and higher donor density under the condition of illumination than the rough film. On account of those, smooth film exhibits comparatively higher anodic and cathodic reaction activities and more excellent and stable photocathodic protection to the counter.